1. Field of the Invention
The present invention relates to a piezoelectric actuator for a liquid transporting apparatus which transports a liquid, a liquid transporting apparatus provided with a piezoelectric actuator, and a method of producing piezoelectric actuator.
2. Description of the Related Art
An ink-jet head which discharges ink from nozzles onto a recording medium such as a recording paper is an example of a liquid transporting apparatus which transports a liquid by applying pressure to the liquid. Such an ink-jet head includes a piezoelectric actuator which is arranged on one surface of a channel unit provided with a plurality of pressure chambers communicating with the nozzles respectively, and which changes selectively volume of the pressure chambers (see, for example, U.S. Patent Application Publication No. US2004/119790 A1 corresponding to Japanese Patent Application Laid-open Publication No. 2004-136668; U.S. Pat. Nos. 5,754,205 and 5,922,218 corresponding to Japanese Patent Application Laid-open Publication No. 9-156099; and US Patent Application Publication No. US2004/0060969 A1).
A piezoelectric actuator of an ink-jet head described in U.S. Patent Application Publication No. US2004/119790 A1 includes a piezoelectric layer (piezoelectric sheet) arranged continuously over the pressure chambers, a plurality of individual electrodes formed corresponding to the pressure chambers respectively, on a surface of the piezoelectric layer, and a common electrode sandwiching the piezoelectric layer between the individual electrodes and the common electrode. A plurality of land portions are formed on the plurality of individual electrodes respectively, and a contact portion of a flexible printed circuit (FPC) is electrically connected to the plurality of land portions. Further, a drive voltage is applied selectively to the individual electrodes from a drive unit (driver IC) via the FPC.
On the other hand, in an ink-jet head described in U.S. Pat. Nos. 5,754,205 and 5,922,218, a plurality of drive electrodes (upper drive electrodes and lower drive electrodes) are formed on the surface of a piezoelectric layer (piezoelectric film) which is arranged continuously over the pressure chambers (pressurizing chambers), and a wiring is extended from each of these drive electrodes. The plurality of wirings are drawn in one predetermined direction in a wiring area adjacent to a displacement area on the surface of the piezoelectric layer. In the wiring area, the drive electrodes are arranged and are connected to a printed circuit. In this case, in order to prevent, when a voltage is applied to the drive electrodes, the generation of excessive electrostatic capacitance (parasitic capacitance) between the piezoelectric layer sandwiched between the wirings and the drive electrodes, a low dielectric layer is provided at the wiring area between the piezoelectric layer and the wires.
Further, in an ink-jet head described in U.S. Patent Application Publication No. US2004/0060969 A1, a flexible printed circuit is connected to a plurality of head terminals of the ink-jet head. The flexible printed circuit includes an insulating member in the form of a flexible belt, a plurality of terminal lands which are arranged in a row on one surface of the insulating member, corresponding to a plurality of head terminals of the ink-jet head, and a plurality of lead wirings each of which is wired independently to one of the terminal lands, on the surface of the insulating member where the terminal lands are arranged in a row. Through holes, penetrating through the insulating member, are formed at positions in each of which one of the terminal lands of the insulating material is arranged. Through these through holes, the terminal lands are respectively exposed to other surface of the insulating member. After filling an electroconductive material such as solder into the through holes formed in the insulating member, and positioning the terminal lands of the flexible printed circuit and the head terminals of the ink-jet head to face one another, the terminal lands and the head terminals are connected by the electroconductive material in the through holes. At this time, since the electroconductive material in each of the through holes, a terminal land adjacent to the electroconductive material in one of the through holes, and a lead wiring wired to the adjacent terminal land are isolated from one another by the insulating member, there is no fear of a short circuit.